A coal-fired power generation installation using a pulverized coal-fired boiler has occupied an important role due to recent situations such as price increase of petroleum and natural gas resulting from increased demand thereon. Generally used as a conventional pulverized coal-fired boiler is an air combustion boiler using air as combustion support gas.
Coal combustion itself has a problem of much CO2 emission in comparison with petroleum or natural gas combustion. Thus, increased emission of CO2 due to increased dependence on coal-fired power generation is a serious problem to be avoided from a viewpoint of preventing global warming.
The air combustion boiler, which contains much nitrogen in flue gas, has a problem that troublesome are separation and withdrawal of nitrogen and CO2 from the flue gas.
Thus, an oxyfuel combustion boiler draws attention as means for substantially reducing CO2 emission to the atmosphere and development thereof has been advanced.
Employed in the oxyfuel combustion boiler is flue gas recirculation in which most of flue gas discharged from the pulverized coal-fired oxyfuel combustion boiler is extracted halfway from a gas flue, and the flue gas extracted and mixed with oxygen produced in an oxygen producer and adjusted to have a proper oxygen concentration is supplied as combustion support gas to the oxyfuel combustion boiler. According to the flue gas recirculation type oxyfuel combustion boiler, no nitrogen is contained in the flue gas and a CO2 concentration is dramatically enhanced in the flue gas finally discharged, which facilitate separation and withdrawal of CO2 from the flue gas.
There is, for example, the following Patent Literature 1 which shows general state-of-art technology pertinent to the oxyfuel combustion boiler.